Colicin E8

Colicin E3 is a type of Colicin, a bacteriocin made by E. coli which acts against other nearby E. coli to kill them with its DNase Activity; it digests the host's genome at specific locations, ultimately leading to the death of the cell.

Synthesis and release
The ColE8 operon is encoded on a plasmid in the E. coli cell, and includes the gene encoding Im8, its Colicin Immunity Protein. When the colicin has been synthesised, the immunity protein binds to the cytotoxic domain, to protect the colicinogenic cell from the killing activity.

Mechanism of uptake
The receptor domain of ColE8 binds to BtuB, the vitamin B12 outer membrane receptor of the target cell, triggering the dissociation of Im8 from the cytotoxic domain. Once bound, OmpF and the TolQRAB complexes are recruited and bind to the translocation domain, triggering the translocation of the colicin across the membrane, using a currently unidentified mechanism.

Killing Activities
ColE8 kills the targeted E. coli cell with its DNase Activity, where it is able to digest the genome at a number of locations. This triggers the SOS response in the host cell, ultimately leading to the death of the cell.